This type of drainable collecting bags is often used as ostomy bags. In the case of ileostomy patients and colostomy patients with uncontrolled release of faeces of a more or less fluid consistence, the collecting bag has to be emptied rather frequently, and the closure device thus has to be easy to open and re-close after emptying and at the same time provide a reliable and tight seal in operation, i.e. between emptyings.
Several different designs of closure devices have been developed and are generally known.
Published international application No. WO 99/66859 discloses a collecting bag having one or more resilient seal members positioned at or near the discharge opening. The resilience of the member or members provides an efficient sealing effect at the beginning and the end, respectively, of the folding operation.
In a further development of this collecting bag usable in a wider range of applications, published international application No. WO 2004/030584 discloses a collecting bag of the kind mentioned in the introduction. The collecting bag disclosed in this document provides for a combination of forming the plate members from a relatively stiff material and particular positions of the plate members with respect to each other, by which the effect is obtained that the folding operation is facilitated even in case of wide discharge portions. Surprisingly, it turns out that sufficient tightness is achieved, even though virtually no deformation of the plate members in the thickness direction takes place. During the folding of the discharge portion the distal edge of the first plate member provides a pivot which, due to the thickness of the first plate member in combination with the small distance between this distal edge and the proximal edge of the second plate member, gives rise to a tensional force in the longitudinal direction of at least the second film blank and consequently, the elasticity of the film blanks provides a sealing force.
This collecting bag has proven to function well. However, the position of the plate members is relatively important in order to ensure proper function of the collecting bag and consequently, particular measures have to be taken during manufacture to secure that the plate members are positioned correctly.